The biggest problem I see with this is that it makes INT a very important stat for ALL spell casters. Unless I'm missing something, Clerics', Druids', Paladins' and Rangers' spell ability is not based on Wisdom in anyway and Bards and Sorcerers do not depend on Charisma at all...except maybe in determining the save DC of their spells, but if a caster is going to concentrate on spells that have no save(like boosting and healing spells), then it doesn't matter...
I would suggest somehow seperating normal skill points and spell skill points and applying the bonus from the appropriate ability score for the class. Or making the Spellcraft check when casting spells use the bonus from the appropriate score rather than INT. So when a cleric casts a spell, his spellcraft check is modified by Wisdom rather than Int.
What is the effect on metamagic feats? Particularly the Quicken Spell feat...normally that is only available to classes that prepare spells. It appears there is no spell preparation so would that feat just no longer have any function?
My biggest problem with it is the complexity. As a DM, I would dread trying to "make up" a spell casting NPC on the fly, even a low level one. Modifying spellcasters in pre-fab adventures would be quite a chore as well. I would presume that your goal would be to balance your system with the normal one so that a spell caster from each system would be roughly equal(so that you wouldn't HAVE to redo every NPC spell caster in the game.
